The present invention relates to a method of manufacturing a magneto-resistive effect element and a method of manufacturing a magneto-resistive effect type magnetic head.
In recent years, a recording density is progressively increased in the field of the magnetic recording and magneto-resistive effect type magnetic heads (MR type magnetic heads) using a giant magneto-resistive effect (GMR) element as a magnetic sensing portion are now put into practical use. Lately, those magneto-resistive effect type magnetic heads have achieved a recording density in excess of 50 Gb/inch2 (e.g., Intermag Conference 2000: Fujitsu, Read-Rite).
In such magnetic head, the MR element portion has a so-called CIP (Current In-Plane) type structure capable of detecting a magnetic field by an electrical resistance change occurring when a sense current is usually conducted in a film plane direction and an external magnetic field, i.e., a signal magnetic field corresponding to recorded information from a magnetic recording medium is applied to the film plane in parallel thereto.
On the other hand, with the increasing demand for a higher recording density, it has been requested that the elements are microminiaturized by selecting materials composing the MR element portion which can realize a high sensitivity and by using a high-precise patterning, to be specific, a photolithography technique which can reduce a track width.
In contrast, as a magneto-resistive element which can exhibit a larger resistance change, there has been proposed based on a CPP (Current Perpendicular to Plane) type structure a spin valve type MR (SV type GMR) element or a tunnel type MR (TMR) element in which a sense current is conducted in the direction perpendicular to the film plane of the MR element.
Of the MR element of this CPP type structure, the SV type GMR element can be realized by a film structure substantially similar to that of the conventional CIP type. Specifically, this magneto-resistive effect element includes two ferromagnetic layers separated by a spacer layer formed of a thin nonmagnetic conductive layer and makes use of a resistance change based upon an electron spin dependent scattering caused on these interfaces.
In this case, one of the ferromagnetic layers is made of a material whose saturation coercive force is larger than that of the other ferromagnetic layer, and so has a high saturation magnetic field.
Further, in this structure, the film thicknesses of the respective layers are optimized depending on mean free paths of electrons in the respective layers so that the amount of the resistance change may be increased.
The magnetic response of this MR element is a function depending upon a relative magnetization direction between the two ferromagnetic layers.
On the other hand, the TMR type element includes two ferromagnetic layers separated by a spacer comprised of a thin insulating tunnel barrier layer and makes use of a resistance change caused by a magnetic polarization electron tunnel phenomenon.
One of these ferromagnetic layers has typically a saturation magnetic field which is higher than that of the other ferromagnetic layer in one direction.
Then, its insulating tunnel barrier layer has a film thickness which is thin enough to make a quantum mechanics tunnel phenomenon occur between the two ferromagnetic layers. This tunnel phenomenon depends upon an electron spin, whereby a magnetic response of a tunnel type element depends upon a relative magnetization direction of the above-described two ferromagnetic layers and a function of a spin polarity.
Because the SV type GMR element and TMR element in the CPP structure have a still larger amount of resistance change as compared with that of the MR element in the above-mentioned CIP structure, a highly-sensitive MR type magnetic head can be realized theoretically.
By the way, when data is recorded at a higher recording density, e.g., 100 Gb/inch2, in order to detect narrow magnetic recording patterns having a width less than 0.1 xcexcm, it is requested to realize a highly-precise MR element.
There has been proposed a method of manufacturing a microminiaturized MR element as what element which can meet with such requirements.
In a method of manufacturing such a microminiaturized MR element, particularly, a MR element including a magnetic flux guide layer, the microminiaturized MR element manufacturing process involves a process for simultaneously patterning a portion having a multilayer film of different materials, particularly, a multilayer structure of an insulating layer, e.g., aluminum oxide or silicon oxide and a metal layer, and a multilayer structure portion formed by a multilayer of substantially only metal layers.
This patterning can be executed by ion beam etching method for example. In this case, because etch rates of aluminum oxide or the silicon oxide of the above-mentioned insulating layer and the metal layer are remarkably different from each other, there arises a problem that a micro miniaturized MR element having an aimed structure cannot be manufactured with a satisfactory yield.
It is an object of the present invention to provide a method of manufacturing a magneto-resistive effect element and a method of manufacturing a magneto-resistive effect type magnetic head which can solve the above-mentioned problem and can produce a microminiaturized MR element having an aimed structure with high reliability.
A method of manufacturing a magneto-resistive effect element according to the present invention is a method of manufacturing a magneto-resistive effect element having a multilayer structure portion in which there are piled at least a magnetic flux guide layer, a free layer made of a soft magnetic material of which there are piled the magnetization is rotated in response to an external magnetic field, or the free layer also acting as the magnetic flux guide layer a fixed layer made of a ferromagnetic material, an antiferromagnetic magnetic layer for fixing the magnetization of the fixed layer and a spacer layer interposed between the free layer and the fixed layer, namely, an SV type GMR multilayer structure portion or a TMR multilayer structure portion.
This manufacturing method comprises a film forming process for forming a multilayer film including at least the antiferromagnetic layer, the fixed layer and the spacer layer, a first patterning process for patterning this multilayer film after a predetermined pattern, e.g., a pattern having a predetermined depth length, a process for filling up the circumference of the multilayer film thus patterned with an insulating layer, a process for forming the magnetic flux guide layer or the free layer also acting as the magnetic flux guide layer over this insulating layer and the patterned multilayer film, and a second patterning process for patterning simultaneously the magnetic flux guide layer and the above-mentioned multilayer film after a predetermined pattern, e.g., a pattern having a predetermined width to form the above-mentioned multilayer structure portion by beam etching.
Moreover, according to the present invention, when the MR element including the magnetic flux guide layer is formed, the first patterning for determining the depth of the MR element body, i.e., the above-mentioned SV type GMR multilayer structure portion or the TMR multilayer structure portion and the second patterning for determining the widths of the MR element body and the magnetic flux guide layer are executed by etching in such a manner that the materials comprising the above-mentioned multilayer structure portion and the materials comprising the above-mentioned insulating layer at approximately equal the same etch rate. This is done by selecting an incident angle of an etching beam. To be concrete, if the above-mentioned insulating layer is, e.g. silicon oxide, an angle xcex8 relative to a normal of an etched plane is selected in the range of 10xc2x0xe2x89xa6xcex8xe2x89xa640xc2x0, preferably, 15xc2x0xe2x89xa6xcex8xe2x89xa635xc2x0.
Furthermore, in the method of manufacturing the magneto-resistive effect type magnetic head according to the present invention, the magneto-resistive effect element forming its magnetic sensing portion is manufactured by the above-mentioned magneto-resistive effect element manufacturing method.
As described above, in the present invention, the SV type GMR multilayer structure portion is, as it were, a metallic multilayer structure portion, whereas the TMR multilayer structure portion includes, e.g. aluminum oxide Al2O3 forming the tunnel barrier layer interposed as the spacer layer. However, this insulating layer is a extremely thin insulating layer having a thickness of about 0.6 nm, so that the TMR multilayer structure portion has substantially a metallic multilayer structure. For this reason, when the magnetic flux guide layer extending over the metallic multilayer portion and the insulating layer is etched together with the insulating layer, it is arranged that nearly equal etch rates are obtained by selecting the incident angle xcex8 of the etching beam. This allows the etching depth of the above-mentioned multilayer structure portion and its circumference to be made exactly equal. Therefore, the position of the hard magnetic layer which is bias-magnetized for the free layer that will be formed on this etched portion later on can be determined with high accuracy.